Valve for controlling fluids

ABSTRACT

A valve for controlling fluids having a piezoelectric actuator unit which has an actuator base and an actuator head that acts on a coupling module which is connected to a valve closing member that cooperates with a valve seat; the actuator base is braced via a spherical face on a conical seat of a valve housing and has an O-ring seal on its circumference. The spherical face of the actuator base is located on the side of the O-ring seal facing away from the actuator head.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a 35 USC 371 application of PCT/DE 2004/000568 filedon Mar. 19, 2004.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention is directed to an improved valve for controlling fluids,and more particularly to such a valve which may be used in a fuelinjection system.

2. Description of the Prior Art

One valve known from German Patent Disclosure DE 101 40 529 A1 can beused for instance in a fuel injection valve, in particular in a commonrail injector of a diesel internal combustion engine of a motor vehicle.

The valve known from DE 101 40 529 A1 includes a piezoelectric actuatorunit, which has an actuator base and an actuator head. The actuator baseis braced, via a rounded, annular edge, on a conical seat that isembodied on a valve housing. The actuator head acts on a couplingmodule, which includes a so-called adjusting piston which is connectedto the actuator head and is operatively connected to a so-calledactuating piston via a hydraulic coupler. The actuating piston acts on avalve closing member, which cooperates with a valve seat and by means ofwhich a stream of fluid can be controlled.

Because the actuator base is supported on the spherical face of thevalve housing via the rounded edge, tolerance-dictated skewed positionsand assembly-dictated shifting of the actuator head can be compensatedfor. For sealing purposes, an O-ring is supported in an annular groovein the region of the actuator base. As viewed from the direction of theactuator head, the O-ring is located behind the rounded edge.

The structural group formed of the piezoelectric actuator unit and thecoupling module forms a valve control unit of the fuel injection valveand serves to control a nozzle needle, which is located in an injectormodule of the fuel injection valve and cooperates with injectionopenings that lead to a combustion chamber of the engine.

In the installation of the known valve, the actuator base is prestressedby a spring sleeve, which surrounds the coupling module, with a force ofapproximately 700 N. Upon compensation for a tolerance-dictated skewedposition and assembly-dictated shifting of the actuator head, africtional moment occurs in the region of the rounded edge, which actsas a ball bearing. This frictional moment generates bending stresses,which can lead to damage, in the piezoelectric actuator unit.

To avoid leaks in the region of the O-ring seal, the regions of theactuator base that define the annular groove for the O-ring are locatedin the valve housing with a slight lateral play. The slight playdisadvantageously means that the possible rotation of the actuator baseis very slight, and as a result it may not be possible to compensateadequately for the incident tolerance-dictated rotations andassembly-dictated shifting of the actuator head.

Moreover, there is the problem in the known valve that the O-ring mustbe stretched greatly to be installed in the annular groove; on the onehand, this means increased effort in installation and on the other itcan lead to increased rotation of the O-ring, and this rotation candisadvantageously cause leaks.

SUMMARY AND ADVANTAGES OF THE INVENTION

The valve for controlling fluids of the invention in which valve thespherical face of the actuator base is located behind the O-ring seal asviewed from the direction of the actuator head, has the advantage thatcompared to the known valve described above, by suitably locating thespherical face in the region of the ball bearing or the rounded edge, asmaller friction radius can be achieved, which causes less moment ofresistance in the bearing region. In the event of tolerance-causedrotation and assembly-dictated shifting of the actuator head, this meansa lesser bending moment that is exerted on the piezoelectric actuatorunit. The friction radius and the incident bending stresses in thepiezoelectric actuator unit can be reduced by up to 50%, compared to theknown valve.

The valve for controlling fluids of the invention in particular forms avalve control unit of a fuel injection valve, in particular a commonrail injector of an internal combustion engine of a motor vehicle.

In a preferred embodiment of the valve of the invention, the O-ring sealis slipped onto a region of the actuator base of reduced diameter. TheO-ring seal, which preferably has an inside diameter that is slightlysmaller than the diameter of the region of the actuator base having thereduced diameter, can thus be installed simply and securely, since therisk of rotation of the O-ring during assembly, which candisadvantageously cause leaks, is reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

One exemplary embodiment of the valve of the invention is described morefully herein below, in conjunction with the drawings, in which:

FIG. 1 shows a longitudinal section through a valve of the invention, ina fragmentary view; and

FIG. 2 shows an enlarged view of the region II outlined in dashed linesin FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In FIGS. 1 and 2, a valve control unit 1 is shown of a fuel injectionvalve which serves as a common rail injector for injecting preferablydiesel fuel into a combustion chamber of a diesel internal combustionengine, not shown further here, of a motor vehicle.

The fuel injection valve includes, besides the valve control unit 1, anozzle module, not further shown, in which an axially displaceablenozzle needle is located that is operatively connected to so-calledinjection openings that lead to the combustion chamber of the engine.The valve control unit 1 serves to actuate the nozzle needle.

The valve control unit 1 includes a valve housing 2, in which an axiallyoriented fuel supply conduit 3, which leads to the nozzle module, isembodied along with a receiving chamber 4 for a piezoelectric actuatorunit 5 and a hydraulic coupling module 6.

The piezoelectric actuator module 5 includes a piezoelectric actuator 7,which is located between an actuator base 8 and an actuator head 9. Toprotect against fuel, the piezoelectric actuator unit 5 is encapsulated,specifically by means of both a tubular sleeve 10, solidly joined to theactuator base 8, and a bellows diaphragm 11 which surrounds the actuatorhead 9 and is joined to the sleeve 10 and is designed to receive anaxial bearing of the piezoelectric actuator 7.

The actuator head 9, which serves to transmit the change in length ofthe piezoelectric actuator 7 to the coupling module 6, engages a disk13, which is provided with a corresponding recess 12 and is solidlyjoined to an adjusting piston 14 of the coupling module 6, which pistonis in turn coupled, via a hydraulic coupler, not shown, embodied as ahydraulic chamber, to an actuating piston, also not shown. The actuatingpiston is connected in turn to a valve closing member, which cooperateswith a valve seat and upon whose actuation a change in pressure takesplace in a valve control chamber of the nozzle module, as a result ofwhich the nozzle needle experiences an axial displacement, so that theinjection openings are opened and closed.

The coupling module 6 further includes a spring sleeve 15, by means ofwhich prestressing of the piezoelectric actuator module 5 takes place ata force of approximately 700 N.

The actuator base 8, which is shown in further detail in FIG. 2, isembodied in graduated form and includes a first region 16, directlyadjoining the piezoelectric actuator 7, whose diameter is approximatelyequivalent to that of the piezoelectric actuator 7 and which changesover into a second region 17 of medium diameter, which is in turnadjoined by a third region 18 of reduced diameter. An O-ring seal 20 ispressed or slipped onto the region of reduced diameter and rests on thewall of the valve housing 2. The third region 18 of reduced diameter ofthe actuator base 8 has a diameter D1 which is somewhat greater than theinside diameter of the O-ring 20, so that the latter is seated securelyon the third region 18 of reduced diameter of the actuator base 8.

The third region 18 of reduced diameter of the actuator base 8 isadjoined, in the direction facing away from the piezoelectric actuator7, by a curved face or spherical face 21, embodied as a ball bearing,which is braced on a conical seat 22 that is embodied on the valvehousing 2. The spherical face 21 is defined by a radius DR, known as afriction radius, and tilting of the actuator base 8 about a pivot pointX can occur.

Between the second region 17 of medium diameter of the actuator base 8and the wall of the valve housing 2, a gap S is embodied, which can beselected to be large enough that any tolerance-dictated rotation and/orassembly-dictated shifting of the actuator head 9 in the radialdirection that may occur, events that are represented in FIG. 1 asexamples by a double arrow marked Y, can be compensated for. This effectis also contributed to by a small spacing A, which is embodied betweenthe pivot point X and the transition between a cylindrical region 23 ofreduced diameter of the receiving chamber 4 and a conical region 24 ofthe receiving chamber 4.

The foregoing relates to preferred exemplary embodiments in theinvention, it being understood that other variants and embodimentsthereof are possible within the spirit and scope of the invention, thelatter being defined by the appended claims.

1. For use in a valve for controlling fluids, a piezoelectric actuatorunit which has an actuator base and an actuator head that acts on acoupling module, wherein the actuator base includes a spherical facewhich is braced against a conical seat of a valve housing and whichactuator base has an O-ring seal on its circumference, wherein thespherical face of the actuator base is located on the side of the O-ringseal facing away from the actuator head.
 2. The valve as recited inclaim 1, further comprising a region of reduced diameter of the actuatorbase, and wherein the O-ring seal is slipped onto the region of reduceddiameter.
 3. The valve as recited in claim 2, wherein the O-ring sealhas an inside diameter which is slightly smaller than the diameter ofthe region of reduced diameter of the actuator base.